Just a thought, many years ago I saw, as a child,youth, a film titled " San Demitrio, London " It was of course in B/W and told the story of a Tanker on a voyage from US to UK and she gets torpedoed,crew take to the boats, drift around for a few days, find the ship again, get her going and get to London, after sinking the U Boat by gunfire. We heard it was based on a true incident. She was a Liberty ship, so if you could get a copy of that film, lots of details there!! Or maybe I am wrong, great story though!